U.S. patent number 6,235,815 [Application Number 09/215,469] was granted by the patent office on 2001-05-22 for biodegradable polymeric mixtures based on thermoplastic starch.
This patent grant is currently assigned to Bio-tec Biologische Naturverpackungen & Co. KG. Invention is credited to Ernst Grigat, Jurgen Loercks, Winfried Pommeranz, Harald Schmidt, Wolfgang Schulz-Schlitte, Ralf Timmermann.
United States Patent |
6,235,815 |
Loercks , et al. |
May 22, 2001 |
**Please see images for:
( Certificate of Correction ) ** |
Biodegradable polymeric mixtures based on thermoplastic starch
Abstract
For converting native starch or starch derivatives into
thermoplastic starch, added to the starch is at least one
hydrophobic biodegradable polymer. This hydrophobic biodegradable
polymer, which serves as a plasticizer or swelling agent, may be a
polymer selected from the following list: an aliphatic polyester, a
copolyester with aliphatic and aromatic blocks, a polyester amide,
a polyester urethane, a polyethylene oxide polymer and/or a
polyglycol, and/or mixtures of these. When the starch, such as in
particular native starch or derivatives thereof, is mixed in the
melt with the hydrophobic biodegradable polymer as a plasticizer or
swelling agent, to homogenize the mixture, the water content is
reduced to <1% by weight based on the weight of the mixture.
Inventors: |
Loercks; Jurgen (Rees,
DE), Pommeranz; Winfried (Enger, DE),
Schmidt; Harald (Emmerich, DE), Timmermann; Ralf
(Krefeld, DE), Grigat; Ernst (Leverkusen,
DE), Schulz-Schlitte; Wolfgang (Langenfeld,
DE) |
Assignee: |
Bio-tec Biologische
Naturverpackungen & Co. KG (DE)
|
Family
ID: |
7797496 |
Appl.
No.: |
09/215,469 |
Filed: |
December 18, 1998 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
PCTIB9700749 |
Jun 20, 1997 |
|
|
|
|
Foreign Application Priority Data
|
|
|
|
|
Jun 20, 1996 [DE] |
|
|
196 24 641 |
|
Current U.S.
Class: |
524/47 |
Current CPC
Class: |
B32B
27/10 (20130101); C08J 3/005 (20130101); C08L
3/00 (20130101); C08L 71/02 (20130101); F42B
5/30 (20130101); F42B 12/76 (20130101); C08L
3/00 (20130101); C08L 71/02 (20130101); C08L
2201/06 (20130101); C08L 2666/02 (20130101); C08L
2666/26 (20130101) |
Current International
Class: |
B32B
27/10 (20060101); C08L 71/02 (20060101); C08L
3/00 (20060101); C08L 71/00 (20060101); F42B
5/00 (20060101); F42B 5/30 (20060101); C08J
3/00 (20060101); F42B 12/76 (20060101); F42B
12/00 (20060101); C08J 001/26 () |
Field of
Search: |
;528/176 ;524/47 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
5286770 |
February 1994 |
Bastioli et al. |
5321064 |
June 1994 |
Vaidya et al. |
5453144 |
September 1995 |
Kauffman et al. |
|
Primary Examiner: Boykin; Terressa M.
Attorney, Agent or Firm: Workman, Nydegger & Seeley
Parent Case Text
This is a continuation application of PCT/IB97/00749 filed on Jun.
20, 1997.
Claims
What is claimed is:
1. A polymeric mixture consisting essentially of thermoplastic
starch containing, as a plasticizer responsible for converting at
least one of native starch or a starch derivative into the
thermoplastic starch, at least one hydrophobic biodegradable
polymer selected from the group consisting of aliphatic polyesters,
copolyesters having aliphatic and aromatic blocks, polyester
amides, polyethylene oxide polymers, polyglycols, and mixtures
thereof,
wherein the thermoplastic starch is formed by heating and mixing
the native starch or starch derivative with the biodegradable
polymer in a manner so as to yield a thermoplastic starch melt
having a water content of less than 5% by weight based on the total
weight of the polymeric mixture and prior to cooling the melt.
2. A polymeric mixture as defined in claim 1, wherein the
thermoplastic starch is formed by in situ reaction of the native
starch or starch derivative with the hydrophobic polymer by heating
and mixing in a manner so that the thermoplastic starch melt has a
water content of less than 1% by weight of the polymeric mixture
prior to cooling, and in the optional presence of an additional
plasticizer comprising a low-molecular-weight plasticizer.
3. A polymeric mixture as defined in claim 1, wherein the
hydrophobic biodegradable polymer is included in an amount in a
range from about 10% to about 40% by weight of the polymeric
mixture.
4. A polymeric mixture as defined in claim 1, further including at
least one additional hydrophobic biodegradable polymer.
5. A polymeric mixture as defined in claim 4, wherein the
additional hydrophobic biodegradable polymer is selected from the
group consisting of aliphatic polyesters, copolyesters having
aliphatic and aromatic blocks, polyester amides, polyester
urethanes, polyethylene oxide polymers, polyglycols, and mixtures
thereof.
6. A polymeric mixture as defined in claim 4, wherein the at least
one hydrophobic biodegradable polymer or the at least one
additional hydrophobic biodegradable polymer includes at least one
polymer selected from the group consisting of:
1) aliphatic and partially aromatic polyesters of
A) linear or cycloaliphatic dihydric alcohols and linear dibasic or
cycloaliphatic dibasic acids, or
B) building blocks with acid and alcohol functionalities, or
copolymers of A and B, wherein the aromatic acid content does
exceed 50% by weight based on all of the acids;
2) aliphatic polyester urethanes of
C) esters of linear of cycloaliphatic dihydric alcohols and linear
or cycloaliphatic or aromatic dibasic acids, or
D) esters from building blocks with acid and alcohol
functionalities, or copolymers of C) and D), and
E) reaction products of C) and D) or both with at least one
aliphatic or cycloaliphatic bifunctional isocyanate, wherein the
ester of C) and D) is at least 75% by weight, based on the total of
C), D) and E);
3) aliphatic-aromatic polyester carbonates of
F) esters of linear of cycloaliphatic dihydric alcohols, and linear
or cycloaliphatic dibasic acids, or
G) esters of building blocks with acid and alcohol functionalities,
or copolymers of both F) and G), or
H) carbonates from an aromatic dihydric phenol or a carbonate
donor, wherein the ester fraction F) and G) is at least 70% by
weight, based on the total of F), G) and H);
4) aliphatic polyester amides of
I) esters of linear of cycloaliphatic dihydric alcohols and linear
or cycloaliphatic dibasic acids or,
K) esters of building blocks with acid and alcohol functionalities,
or copolymers of I) and K), and
L) amides of linear of cycloaliphatic dibasic amines, and linear or
cycloaliphatic dibasic acids, or
M) amides of building blocks with acid and amine functionalities,
or mixtures of L) and M), where the ester fraction I) and K) is at
least 30% by weight based on the total of I), K), L) and M).
7. A polymeric mixture as defined in claim 4, wherein the
plasticizer and the additional hydrophobic biodegradable polymer
includes a polyester copolymer of at least one diol selected from
the group consisting of 1,2-ethanediol, 1,3-propanediol,
1,4-butanediol and 1,6-hexanediol, and at least one aromatic
dicarboxylic acid, and optionally at least one aliphatic
dicarboxylic acid.
8. A polymeric mixture as defined in claim 1, wherein the
plasticizer includes a copolyester comprising at least one aromatic
dicarboxylic acid and at least one aliphatic dicarboxylic acid.
9. A polymeric mixture as defined in claim 4, wherein at least one
of the plasticizer or the additional hydrophobic biodegradable
polymer is selected from the group consisting of polylactic acid,
polyhydroxybutyric acid, polyhydroxybenzoic acid,
polyhydroxybutyric acid-hydroxyvaleric acid copolymer, and
polycaprolactone.
10. A polymeric mixture as defined in claim 4, wherein at least one
of the plasticizer or the additional hydrophobic biodegradable
polymer is at least one oligomeric polyester amide with a molecular
weight of at least 300 of at least one monomer selected from the
group consisting of dialcohols, dicarboxylic acids and their
respective esters, hydroxycarboxylic acids and lactones, amino
alcohols, cyclic lactams, .omega.-aminocarboxylic acids, and
mixture of dicarboxylic acids and diamines.
11. A layered film comprising one or more layers of the polymeric
mixture defined in claim 1.
12. A container comprising a blow molded composition of the
polymeric mixture defined in claim 1.
13. An adhesive or coating composition consisting essentially of an
alcoholic solution of the polymeric mixture defined in claim 1.
14. A method for manufacturing a polymeric mixture consisting
essentially of thermoplastic starch, wherein at least one of native
starch or a starch derivative is homogenized while in the form of a
thermoplastic starch melt by means of a plasticizer and in a manner
so that the water content prior to or during heating and mixing of
the thermoplastic starch melt is reduced to less than 5% by weight
based on the weight of the polymeric mixture prior to cooling of
the melt, wherein the plasticizer is at least one hydrophobic
biodegradable polymer selected from the group consisting of
aliphatic polyesters, copolyesters having aliphatic and aromatic
blocks, polyester amides, polyester urethanes, polyethylene oxide
polymers, polyglycols, and mixture thereof.
15. A method for manufacturing a polymeric mixture as defined in
claim 14, wherein the native starch or starch derivative is mixed
in the thermoplastic starch melt with at least one hydrophobic
biodegradable polymer which reacts in situ with the native starch
or starch derivative, thereby forming a reaction product thereof
which serves as a compatibilizer for facilitating formation of a
homogenous polymer melt.
16. A method for manufacturing a polymeric mixture as defined in
claim 14, wherein the water content of the thermoplastic starch
melt prior to or during mixing is reduced to less than about 0.1%
by weight of the polymeric mixture prior to cooling.
17. A method for manufacturing a polymeric mixture as defined in
claim 14, wherein the thermoplastic starch melt is formed within a
temperature range of about 120.degree. C. to about 260.degree.
C.
18. A method for manufacturing a polymeric mixture as defined in
claim 14, wherein the thermoplastic starch melt is formed in at
least one of an extruder or kneader and wherein the thermoplastic
starch melt is drawn off from a die thereof and cooled in a water
bath and conditioned.
19. A method for manufacturing a polymeric mixture as defined in
claim 18, wherein the polymeric mixture is in the form of a
granulate having a maximum water content of about 1% by weight of
the granulate prior to conditioning.
20. A method for manufacturing a blown film which comprises
conditioning granulates of the polymeric mixture defined in claim 1
with a plasticizer and then conducting a blow-extrusion
process.
21. A method for manufacturing a blown film as defined in claim 20,
wherein the granulates are conditioned to a water content in a
range from about 1% to about 6% by weight of the granulates and
then blown-extruded to yield a film.
22. A method for manufacturing a film having one of more layers of
the polymer mixture defined in claim 1, wherein plasticization of
the thermoplastic starch and subsequent production of the film
takes place continuously and in a single process.
23. A polymeric mixture as defined in claim 8, wherein the aromatic
dicarboxylic acid includes terephthalic acid and the aliphatic
dicarboxylic acid includes at least one of adipic acid or sebacic
acid.
24. A polymeric mixture as defined in claim 1, wherein the
polymeric mixture has a water content of less than about 0.5% by
weight of the polymeric mixture while in a melted state and prior
to cooling.
25. A polymeric mixture as defined in claim 1, wherein the
polymeric mixture has a water content of less than about 0.1% by
weight of the polymeric mixture while in a melted state and prior
to cooling.
26. A polymeric mixture as defined in claim 1, wherein the
polymeric mixture has been conditioned, upon cooling of the
thermoplastic starch melt, to a water content in a range from about
1% to about 6% by weight of the polymer mixture.
27. A polymeric mixture as defined in claim 1, wherein the
polymeric mixture has been conditioned, upon cooling of the
thermoplastic starch melt, to a water content in a range from about
0.3% to about 4% by weight of the polymer mixture.
28. A method for manufacturing a polymeric mixture as defined in
claim 14, wherein the water content of the thermoplastic starch
melt prior to or during mixing is reduced to less than about 1% by
weight of the polymeric mixture prior to cooling.
29. A method for manufacturing a polymeric mixture as defined in
claim 14, wherein the water content of the thermoplastic starch
melt prior to or during mixing is reduced to less than about 0.5%
by weight of the polymeric mixture prior to cooling.
30. A method for manufacturing a polymeric mixture as defined in
claim 14, further including cooling the thermoplastic starch melt
and conditioning the polymeric mixture to a water content in range
from about 1% to about 6% by weight of the polymeric mixture.
31. A method for manufacturing a polymeric mixture as defined in
claim 14, further including cooling the thermoplastic starch melt
and conditioning the polymeric mixture to a water content in range
from about 0.3% to about 4% by weight of the polymeric mixture.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a biodegradable polymeric material
essentially consisting of, or based on, thermoplastic starch, and
to a polymer mixture comprising thermoplastic starch, a process for
preparing a biodegradable material, a process for preparing a
polymer mixture, and also to uses of the biodegradable material and
of the polymer mixtures comprising thermoplastic starch.
Biopolymers based on renewable raw materials which are suitable for
preparing biodegradable materials (BDM) are largely based on starch
and comprise in particular thermoplastic starch, and also polymer
mixtures made from thermoplastic starch and from other degradable
polymeric components, such as polylactic acid, polyvinyl alcohol,
polycaprolactone, tailored copolyesters made from aliphatic diols
and from aliphatic or aromatic dicarboxylic acids, and also
degradable polyester amides, which, with thermoplastic starch in an
anhydrous melt via ester reactions and/or as polymer combinations
form new degradable polymeric materials with a high proportion of
renewable raw materials. There may be addition of other naturally
occurring materials as additives and plasticizers such as glycerol
and its derivatives, and hexahydric sugar alcohols such as sorbitol
and derivatives of these.
EP 397 819 has for the first time specified a process for preparing
TPS and also defined the new starch material known as thermoplastic
starch (TPS) and specified the important differences, in particular
in plastics processing technology, from the destructured starch
which has been known for a relatively long time.
The thermoplastic starch is prepared with the aid of a swelling
agent or plasticizer, not only without adding water but more
particularly using dry or dried starch and/or starch which has been
dried by devolatilization during the extrusion process while in the
melt. Starches in the form of native starches commercially
available comprise 14% of water, and potato starch as much as 18%
of natural moisture at equilibrium.
If a starch with more than 5% of moisture is plasticized or pasted
with exposure to temperature and pressure, this always gives a
destructured starch. The preparation of the destructured starch is
an endothermic procedure.
In contrast, the preparation of the thermoplastic starch is an
exothermic procedure. In this case the essentially anhydrous
(<5%) native starch is homogenized in an extrusion process with
an additive or plasticizer (e.g. glycerol, glycerol acetate,
sorbitol) which lowers the melting point of the starch, and is
melted within a temperature range of from 120 to 220.degree. C. by
introducing mechanical energy and heat. The thermoplastic starch is
free from crystalline fractions, or at least the crystalline
fractions are less than 5% in the TPS, where the crystalline
fractions remain unchanged and very small. The parameters of the
process bring about a permanent rearrangement of the molecular
structure to give thermoplastic starch, which now comprises
practically no crystalline fractions and, contrasting with
destructured starch, does not now recrystallize.
In destructured starch, the crystalline fractions immediately after
preparation are likewise small, but these increase again when
destructured starch is stored. This feature is also apparent in the
glass transition temperature, which for thermoplastic starch
remains at -40.degree. C., whereas in destructured starch, in
contrast, it rises again to above 0.degree. C. For these reasons,
destructured starch and materials or blends based on destructured
starch gradually become relatively brittle on storage, and,
depending on temperature and time elapsed, the stresses contained
within the polymer cause creep and distortion of the material
(memory effect).
A differentiation of destructured starch and thermoplastic starch
is:
Preparation Destructured Thermoplastic and properties starches
starches Water content >5 to 50% <5%, preferably anhydrous in
the melt phase Plasticizer Water, glycerol, Glycerol, sorbitol,
Additives sorbitol, glycerol acetate, mixtures essentially
anhydrous Crystalline >>5% rising on <<5%, no
crystalline fractions storage fractions, unchanged on storage
Preparation Endothermic Exothermic process Glass >0.degree. C.
<-40.degree. C. transition temperature Storage Increasing
Remains flexible properties embrittlement Analytical X-ray X-ray
diffraction of differentiation diffraction of the crystalline the
crystalline fractions fractions
When polymer mixtures based on thermoplastic starch are prepared,
compatibilizers are used to homogenize the hydrophilic and polar
starch polymer phase and the hydrophobic and nonpolar other polymer
phase, which are either added or preferably are produced in situ
(e.g. by transesterification)ecified temperature and shear
conditions, to give processable granules. The technology of
preparing these thermoplastic blends involves coupling together the
phase boundaries between the low-compatibility polymers in such a
way as to achieve the distribution structure of the disperse phase
during processing via the ideal range of processing conditions
(temperature and shear conditions).
The twin-screw extruders which, for example, are used for the
compounding are preferably corotating twin-screw extruders with
tightly intermeshing screw profile and kneading zones which can be
individually temperature-controlled. The twin-screw extruders used
for the TPS compounding or preparation of TPS/polymer blends
preferably have eight compartments or zones which where appropriate
may be extended to ten zones and have, for example, the following
construction:
Extruder design: Corotating twin-screw extruder, for example
Screw length-processing length = 32-40 L/D Screw diameter D = 45 mm
Screw rotation rate = 230 rpm Throughput = 50-65 kg/h Die, diameter
= 3 mm Die, number = 4 Zone 1 Compressing with Feed zone temp.
60.degree. C. devolatilization, Pressure - bar gradual melting of
the mixture (native and glycerol) Zone 2 as Zone 1 Mixing and
plasticization Temp. 140.degree. C. Pressure >1 bar Water
content 4-7% Zone 3 as Zone 1 Plasticization Temp. 180.degree. C.
Pressure >1 bar Water content 4-7% Zone 4 as Zone 1
Plasticization Temp. 185.degree. C. Pressure >1 bar Water
content 4-7% Zone 5 Devolatilization, water extraction Temp.
160.degree. C. Pressure vacuum 0.7 bar Water content <1% Zone 6
(Side feeder, metering- Metering-in of other in of the additional
polymers polymers, such as PCL) Temp. 200.degree. C. Pressure >1
bar Water content <1% Zone 7 Transition zone, Homogenization and
where compression zone, appropriate transesteri- reaction zone
fication Temp. 200.degree. C. Pressure >1 bar Water content
<1% Zone 8 Metering zone, where Homogenization and where
appropriate evaporation appropriate transesteri- of water of
reaction fication Temp. 205-210.degree. C. Pressure >1 bar Water
content <1%
Outside the extrusion plant: cooling and conditioning of the
extrudates, where appropriate absorption of from 0.3 to 4% of water
as plasticizer in a water bath, extrudate granulation, and
bagging.
The extrusion conditions given above for preparing thermoplastic
starch or mixtures based on thermoplastic starch are substantially
directed toward the example of a TPS/PCL (polycaprolactone) polymer
mixture. The processing or extrusion conditions change, of course,
for polymer mixtures of other types. The example given above is
intended merely to show how the prior art prepares polymer mixtures
based on thermoplastic starch.
In connection with the original German Patent Application DE
19624641.5, in which the present invention was presented for
purposes of a priority application, the relevant search by the
German Patent Office mentioned the following publications:
Kunststoffe 82 (11), pp. 1086-1089 (1992), WO95/33874, WO94/28029,
WO94/03543, EP 580 032, EP 404 727, U.S. Pat. No. 5,453,144, U.S.
Pat. No. 5,321,064 and U.S. Pat. No. 5,286,770. All of the
publications mentioned, insofar as they refer to starch, relate to
native starch or destructured starch, i.e. they have no connection
with thermoplastic starch of the type defined at the outset.
In the case of all of the polymer mixtures or polymers described in
the prior art and comprising thermoplastic starch or based on
thermoplastic starch, the assumption is made that the thermoplastic
starch is initially created by conversion from native starch with a
very substantially low-molecular-weight plasticizer or swelling
agent. In the example given above, the TPS is prepared in Zones 1
to 4. Only subsequently, where appropriate, are other components
mixed either purely physically or even to some extent chemically
with the thermoplastic starch prepared in this way. In the example
given above, an esterification or a transesterification reaction
takes place during mixing of the PCL and the TPS, and the
homogenization therefore also includes a chemical reaction. The
additives and plasticizers which have been proposed and used
hitherto, and which lower the melting point of the starch and have
adequate solubility parameters, are, as mentioned,
low-molecular-weight additives such as, inter alia, DMSO,
butanediol, glycerol, ethylene glycol, propylene glycol, a
diglyceride, diglycol ether, formamide, DMF, dimethylurea,
dimethylacetamide, N-methylacetamide, polyalkene oxide, glycerol
mono- or diacetate, sorbitol, sorbitol esters and citric acid.
Use has also been made on occasions of PVOH, EVOH and derivatives
of these, and also of urea and urea derivatives.
In the original Patent EP 397 819, the solubility parameter of the
plasticizer must be in the required range in order that the
function is fulfilled. This is the important factor in the
preparation of the thermoplastic starch, that the water removed is
substituted by a plasticizer, so that the decomposition temperature
of the starch is lowered on conversion to thermoplastic starch or
thermoplastically processed starch to a sufficient extent so that
the mixing in the melt takes place below the relevant decomposition
temperature of the starch.
SUMMARY OF THE INVENTION
Entirely unexpectedly, it has now been found that polymers, such as
polyester amides, aliphatic polyesters and copolyesters, and also a
large number of other polymers specified below, can take on this
function. This now brings with it the important advantage that
when, in particular, polymer mixtures are prepared which are based
on thermoplastic starch or TPS, the TPS does not firstly have to be
prepared by conversion from native starch using a
low-molecular-weight plasticizer before the other polymer is
metered into it. In contrast, the polymer mixture can be prepared
directly in what amounts to a single operation, by mixing native
starch or starch derivatives with the additional preferably
biodegradable hydrophobic polymer under dry conditions in the melt,
where the starch present therein is thermoplastically processable.
This therefore dispenses with the requirement for initial admixing
of a low-molecular-weight plasticizer, such as glycerol, which the
prior art of necessity proposes.
According to the invention therefore a polymeric material is
proposed, essentially consisting of, or based on, thermoplastic
starch. The thermoplastic starch therefore comprises, as
plasticizer or swelling agent very substantially responsible for
converting native starch or derivatives thereof into thermoplastic
starch, at least one hydrophobic preferably biodegradable
polymer.
DESCRIPTION OF THE INVENTION
Hydrophobic biodegradable polymers which have proven suitable are
in particular aliphatic polyesters, polyester copolymers with
aliphatic and aromatic blocks, polyester amides, polyethylene oxide
polymer or polyglycol, and also polyester urethanes and/or mixtures
of these.
A great advantage of the use of hydrophobic biodegradable polymers
as plasticizers or swelling agents for preparing the thermoplastic
starch is that no volatile and/or water-soluble and/or migratable
plasticizers are present in the thermoplastic starch as is the
case, for example, if low-molecular-weight plasticizers or swelling
agents are used for converting native starch or derivatives thereof
to the thermoplastic starch. Even in cases where use continues to
be made of low-molecular-weight plasticizers or swelling agents,
their proportion can be reduced to a level which is so low that the
disadvantages mentioned can hardly become apparent.
In particular, copolymeric polyesters and polyester amides show
very advantageous improvements in the properties of the
starch/polymer materials, particularly those which have a favorable
effect on the hydrophobic properties. Intermolecular coupling at
the starch-polymer phase and homogeneous distribution of the
polymer particles have an effect on the physical properties. The
hydrophobic properties, in particular, of the starch plastics are
considerably enhanced. Moisture resistance is enhanced and the
tendency of the starch plastics to become brittle is markedly
lowered. However, aliphatic polyesters and polyester urethanes are
also suitable for the conversion of the native starch into
thermoplastic starch. At the same time, the polymers mentioned can
be used as components for mixing with the thermoplastic starch for
preparing biodegradable polymer mixtures.
Possible polymers for mixing with native starch and with starch
derivatives or with thermoplastic starch prepared therefrom are in
particular the following:
Aliphatic and partially aromatic polyesters made from
A) linear dihydric alcohols, such as ethylene glycol, hexanediol or
preferably butanediol, and/or, where appropriate, from
cycloaliphatic dihydric alcohols, such as cyclohexanedimethanol,
and in addition, where appropriate, from small amounts of
higher-functional alcohols, such as 1,2,3-propanetriol or neopentyl
glycol, and from linear dibasic acids, such as succinic acid or
adipic acid, and/or where appropriate from cycloaliphatic dibasic
acids, such as cyclohexanedicarboxylic acid and/or where
appropriate from aromatic dibasic acids, such as terephthalic acid
or isophthalic acid or naphthalenedicarboxylic acid, and, in
addition, where appropriate, from small amounts of
higher-functional acids, such as trimellitic acid, or
B) building blocks with acid and alcohol functionality, for example
hydroxybutyric acid or hydroxyvaleric acid or derivatives of these,
for example .epsilon.-caprolactone,
or from a mixture or from a copolymer made from A and B, where the
aromatic acids do not make up a proportion of more than 50% by
weight, based on all of the acids.
The acids may also be used in the form of derivatives, such as acid
chlorides or esters.
Aliphatic polyester urethanes made from
C) an ester fraction made from linear dihydric alcohols, such as
ethylene glycol, butanediol, hexanediol, preferably butanediol,
and/or where appropriate from cycloaliphatic dihydric alcohols,
such as cyclohexanedimethanol, and in addition, where appropriate,
from small amounts of higher-functional alcohols, such as
1,2,3-propanetriol or neopentyl glycol, and from linear dibasic
acids, such as succinic acid or adipic acid, and/or, where
appropriate, from cycloaliphatic and/or aromatic dibasic acids,
such as cyclohexanedicarboxylic acid and terephthalic acid and, in
addition, where appropriate, small amounts of higher-functional
acids, such as trimellitic acid, or
D) an ester fraction made from building blocks with acid and
alcohol functionality, for example hydroxybutyric acid or
hydroxyvaleric acid or derivatives of these, for example
.epsilon.-caprolactone,
or from a mixture or from a copolymer made from C) and D), and
E) from the reaction product of C) and/or D) with aliphatic and/or
cycloaliphatic bifunctional and, in addition where appropriate,
with higher-functional isocyanates, e.g. tetramethylene
diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate,
and, in addition where appropriate, with linear and/or
cycloaliphatic dihydric and/or higher-functional alcohols, e.g.
ethylene glycol, butanediol, hexanediol, neopentyl glycol and
cyclohexanedimethanol,
where the ester fraction C) and/or D) is at least 75% by weight,
based on the total of C), D) and E).
Aliphatic-aromatic polyester carbonates made from
F) an ester fraction made from linear dihydric alcohols, such as
ethylene glycol, butanediol, hexanediol, preferably butanediol,
and/or from cycloaliphatic dihydric alcohols, such as
cyclohexanedimethanol, and in addition, where appropriate, from
small amounts of higher-functional alcohols, such as
1,2,3-propanetriol or neopentyl glycol, and from linear dibasic
acids, such as succinic acid or adipic acid, and/or where
appropriate from cycloaliphatic dibasic acids, such as
cyclohexanedicarboxylic acid, and, in addition, where appropriate,
from small amounts of higher-functional acids, such as trimellitic
acid, or
G) an ester fraction made from building blocks with acid and
alcohol functionality, for example hydroxybutyric acid or
hydroxyvaleric acid or derivatives of these, for example
.epsilon.-caprolactone,
or from a mixture or from a copolymer made from F) and G), and
H) from a carbonate fraction which is prepared from aromatic
dihydric phenols, preferably bisphenol A, and from carbonate
donors, such as phosgene,
where the ester fraction F) and/or G) is at least 70% by weight,
based on the total of F), G) and H);
Aliphatic polyester amides made from
I) an ester fraction made from linear and/or cycloaliphatic
dihydric alcohols, such as ethylene glycol, hexanediol, butanediol,
preferably butanediol, cyclohexanedimethanol, and, in addition
where appropriate, from small amounts of higher-functional
alcohols, such as 1,2,3-propanetriol or neopentyl glycol, and from
linear and/or cycloaliphatic dibasic acids, such as succinic acid,
adipic acid and cyclohexanedicarboxylic acid, preferably adipic
acid, and, in addition where appropriate, from small amounts of
higher-functional acids, such as trimellitic acid, or
K) an ester fraction made from building blocks with acid and
alcohol functionality, for example hydroxybutyric acid or
hydroxyvaleric acid or derivatives of these, such as
.epsilon.-caprolactone,
or from a mixture or from a copolymer made from I) and K), and
L) from an amide fraction made from linear and/or cycloaliphatic
dibasic amines, and in addition where appropriate from small
amounts of higher-functional amines, for example
tetramethylenediamine, hexamethylenediamine, isophoronediamine, and
from linear and/or cycloaliphatic dibasic acids, and, in addition
where appropriate, from small amounts of higher-functional acids,
such as succinic acid or adipic acid, or
M) from an amide fraction made from building blocks with acid and
amine functionality, preferably .omega.-laurolactam and
particularly preferably .epsilon.-caprolactam,
or from an amide fraction which is a mixture of L) and M), where
the ester fraction I) and/or K) is at least 30% by weight, based on
the total of I), K), L) and M).
In connection with polyester amides, reference may be made in
particular to EP-A 0 641 817, which relates to the preparation and
use of thermoplastically processable and biodegradable aliphatic
polyester amides. In this European patent application, monomers
from the following classes, in particular, are proposed for
synthesis according to the invention of polyester amides:
dialcohols, such as ethylene glycol, 1,4-butanediol,
1,3-propanediol, 1,6-hexanediol, diethylene glycol, etc., and/or a
dicarboxylic acid, such as oxalic acid, succinic acid, adipic acid,
etc., also in the form of their respective esters (methyl, ethyl,
etc.) and/or hydroxycarboxylic acids and lactones, such as
caprolactone, etc., and/or aminoalcohols, such as ethanolamine,
propanolamine, etc., and/or cyclic lactams, such as
.epsilon.-caprolactam or laurolactam, etc., and/or
.omega.-aminocarboxylic acids, such as aminocaproic acid, etc.,
and/or mixtures (1:1 salts) of dicarboxylic acids, such as adipic
acid, succinic acid, etc. and diamines, such as
hexamethylenediamine, diaminobutane, etc.
The ester-forming component may also be hydroxyl- or
acid-terminated polyesters with molecular weights from 200 to
10,000.
The conditions for preparation of the polymer mixtures and polymers
described above can be dispensed with, since their preparation is
very well known from the prior art, for example polyester amides
from the above-mentioned EP-0 641 817.
In connection with compostable polyester urethanes, reference may
also be made to EP 539 975, and therefore any description of their
preparation p with TPS are random copolyesters made from aliphatic
and aromatic dicarboxylic acids with a proportion, for example from
about 35 to 55 mol %, of aromatic acid, such as terephthalic acid.
Polyalkylene terephthalates and polyethylene terephthalates are
examples of copolyesters which have proven suitable for mixing with
TPS.
The above-mentioned hydrophobic biodegradable polymers can be used
on the one hand for converting the native starch or starch
derivatives into thermoplastic starch and also for mixing with the
thermoplastic starch prepared in this way to produce a
biodegradable material based on TPS.
The addition of other additives, such as plasticizers, stabilizers
and flame retardants, and also other biodegradable polymers, such
as cellulose esters, cellulose acetate, cellulose,
polyhydroxybutyric acid, hydrophobic proteins, polyvinyl alcohol,
etc., is possible and again depends on the requirements placed on
the polymer mixture to be prepared, and also, of course, on the
availability of the corresponding components. Other possible
additives are the polymers listed below, gelatine, proteins, zeins,
polysaccharides, cellulose derivatives, polylactides, polyvinyl
alcohol, polyvinyl acetate, polyacrylates, sugar alcohols, shellac,
casein, fatty acid derivatives, vegetable fibers, lecithin,
chitosan, polyester polyurethanes and polyester amides. Mention
should also be made of polyester blends consisting of thermoplastic
starch, the aliphatic/aromatic polyester proposed according to the
invention, and also, as another component, copolymers selected from
the class consisting of ethylene-acrylic acid copolymer and
ethylene-vinyl alcohol copolymer.
Suitable fillers include in particular organic fillers obtained
from renewable raw materials, such as cellulose fibers. Fibers
particularly suitable for reinforcing materials based on TPS or TPS
blends are those of vegetable origin, such as cotton, jute, flax,
sisal, hemp and ramie fiber.
For the preparation of the thermoplastic starch proposed according
to the invention or of biodegradable materials based on
thermoplastic starch, it is important that during mixing of the
native starch with one of the hydrophobic biodegradable polymers
proposed according to the invention, when melting takes place the
water content of the native starch is reduced to less than 1% by
weight. This is necessary so that when mixing the polymer used as
plasticizer or swelling agent the ester groups incorporated into
molecular chains of the hydrophobic polymer undergo esterification
reactions with the native starch in the absence of water. The
molecular chains reacting in this way therefore form, with the
starch, a compatibilizer which permits molecular coupling of the
two phases, i.e. of the hydrophilic starch phase and the
hydrophobic polymer phase, so as to form a continuous phase. If
moisture is present, this reaction suffers competition in that in
the presence of water the ester groups do not react with the starch
to form the compatibilizer but hydrolyze, thus preventing the
formation of a compatibilizer and making it impossible for there to
be satisfactory dispersion or homogenization. If it is made
impossible for the hydrophobic biodegradable polymer used as
plasticizer or swelling agent to mix thoroughly with the native
starch, the necessary conversion of the native starch in order to
prepare the thermoplastic starch cannot take place, and therefore
either the starch becomes destructured or else, if the water
content is too low, molecular degradation of the starch sets in. An
important factor in the conversion of the native starch into
thermoplastic starch is of course, as mentioned at the outset, that
the melting point of the native starch is reduced during mixing
with the plasticizer to such an extent as to prevent molecular
decomposition of the starch. On the other hand, however, the melt
has to be dried so as to prevent the formation of destructured
starch. For this reason, thorough phase mixing of the starch phase
with the hydrophobic polymer phase is necessary as described
above.
The mixing of native starch or derivatives thereof with the
hydrophobic polymer or with hydrophobic block copolymers in the
melt with very substantial exclusion of water forms, as mentioned,
via the in-situ reaction of the starch with the hydrophobic
polymer, the so-called compatibilizer, which may be regarded as an
entity in itself or else as a so-called hydrophobic thermoplastic
starch. Compared with the thermoplastic starch known from the prior
art and prepared using low-molecular-weight plasticizer or swelling
agent, such as glycerol or sorbitol, this hydrophobic thermoplastic
starch has significantly higher water resistance and the water
absorption is, respectively, significantly lower. This hydrophobic
thermoplastic starch prepared in this way can serve as a starting
point for other tailored polymers by adding other biodegradable
hydrophobic polymers.
Besides the native starch preferably used, other suitable raw
materials for preparing the thermoplastically reactive starch are
starch derivatives, such as starch esters, starch ethers and
acid-modified starch. Oxidized starches with an increased content
of carboxyl groups are particularly reactive.
Depending on the hydrophobic biodegradable polymer used, the
processing temperature or melting point during mixing and during
preparation of the thermoplastic starch or of the biodegradable
material may be from about 120 to 260.degree. C., preferably from
140 to 210.degree. C. To allow satisfactory conversion of native
starch into TPS or hydrophobic TPS, it is necessary to add to the
native starch, depending on the hydrophobic polymer used, a
proportion of from 10 to 40% by weight, based on the mixture.
Besides the proportion of swelling agent or plasticizer, further
amounts of the hydrophobic polymer used may also, of course, be
added. The range given of from 10 to about 40% by weight relates
merely to the amount necessary for the conversion.
It has also been found that it can even be advantageous when mixing
the native starch with the hydrophobic biodegradable polymer as
plasticizer to reduce the moisture level to markedly below 1% by
weight, i.e. to a value below 0.5% by weight, or even below 0.1% by
weight, based on the total weight of the mixture. The plasticizer
added ensures that the melting point of the starch is reduced in
such a way that when the melt is produced in order to prepare the
homogeneous mixture, this does not undergo molecular degradation.
It would still be possible, of course, when preparing the
thermoplastic starch or the biodegradable polymeric material, also
to add glycerol, sorbitol or another plasticizer, but this might in
some cases have an effect on the physical and/or mechanical
properties of the material to be prepared. These properties can
generally be improved if the addition of relatively large amounts
of low-molecular-weight plasticizers can be dispensed with.
Examples of possible and preferred polymer mixtures and of
biodegradable materials, at least comprising starch or
thermoplastic starch and a hydrophobic biodegradable polymer, are
listed in Tables 1 to 4 below. These examples are supplemented by a
key in which all of the abbreviations, and also any materials used
in the examples, are described and explained.
These examples, 22 in total, include on the one hand components
which have been used in the sense of plasticizer or swelling agent
for preparing the thermoplastic starch or hydrophobic thermoplastic
starch and on the other hand additional polymeric partners for
mixing with the thermoplastic starch for preparing biodegradable
polymer mixtures proposed according to the invention. These
partners for mixing are likewise hydrophobic biodegradable
polymers. In addition, the tables comprise the processing
conditions and in particular the water content prevailing in the
extruder during the preparation of the polymer mixture. This is in
all cases <0.1% by weight. The tables also give preferred
possible applications for the examples of biodegradable polymeric
materials prepared. Of course, the tables comprise only examples,
and all of the components mentioned at the outset are suitable for
mixing with starch or with thermoplastic starch to prepare
industrially-applicable or non-industrially-applicable polymer
mixtures or biodegradable materials as defined in the
invention.
TABLE 1 Example 1 2 3 4 5 6 7 .sup.1 Starch % 28.7 28.7 28.7 28.7
33.3 33.3 33.3 .sup.1a TIR 2900 % 16.3 16.3 16.3 16.7 -- -- --
.sup.1b TIR 2901 % -- -- -- -- 18.9 -- -- .sup.1c TIR 2905 % -- --
-- -- -- 18.9 -- .sup.1d TIR 2906 A % -- -- -- -- -- -- 18.9 .sup.2
TPS % 45 45 45.0 45.0 52.2 52.2 52.2 H.sub.2 O % <0.1 <0.1
<0.1 <0.1 <0.1 <0.1 <0.1 .sup.3 PLA % -- -- -- 55 --
-- -- .sup.4 Polyamide 1 -- 55 -- -- -- -- -- .sup.5 Polyester 1 --
-- 55 -- -- -- -- .sup.6 PCL % 55 -- -- 47.8 47.8 47.8 .sup.7
Extrusion ZSK ZSK ZSK ZSK ZSK ZSK ZSK 40 40 40 40 40 40 40
T.degree. C. 150 170 200 195 155 210 210 Pressure bar 6.1 8.5 11
6.5 5 7.5 7 MFR g/10' 10 13 9.5 8.5 11 9.7 9.5 Granules 4 mm 4 mm 4
mm 4 mm 4 mm 4 mm 4 mm Granule H.sub.2 O % 0.3 0.2 0.4 0.1 0.2 0.2
0.3 Application Blown film + + + + + + + Flat film + + + + + + +
Sheets + + + + + + + Injection molding + + - + + - - Fibers - - - -
- - -
TABLE 2 Example 8 9 10 11 12 13 14 .sup.1 Starch % 33.3 33.3 52.5
33.3 33.3 33.3 33.3 .sup.1a TIR 2900 % -- -- 23.5 18.9 18.7 18.7
18.7 .sup.1f TIR 2908 -- 18.9 -- -- -- -- -- .sup.2 TPS % 52.2 52.2
76.0 52.2 52.2 52.2 52.2 .sup.3 PLA % -- -- -- -- -- 47.8 -- .sup.4
Polyamide 1 -- -- -- 47.8 -- -- -- .sup.5 Polyester 1 -- -- -- --
47.8 -- 20.0 .sup.6 PCL % 47.8 47.8 24.0 -- -- -- 27.8 H.sub.2 O %
<0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 .sup.7
Extrusion ZSK ZSK ZSK ZSK ZSK ZSK ZSK 40 40 40 40 40 40 40
T.degree. C. 170 170 150 165 210 210 205 Pressure bar 5.5 3.5 8.5
4.0 6.5 8.0 8.5 MFR g/10' 9.5 25 9.5 11.5 9.5 8.5 8.0 Granules 4 mm
4 mm 4 mm 4 mm 4 mm 4 mm 4 mm Granules H.sub.2 O % 0.3 0.2 0.2 0.1
0.2 0.2 0.3 Application Blown film + + + + + + + Flat film + - + +
+ + + Sheets + - + + + + + Injection - - - + - - - molding Fibers -
+ - - - - -
TABLE 3 Example 15 16 17 18 19 20 21 .sup.1 Starch % 20.0 20.0 47.3
33.3 47.3 33.3 51.0 .sup.1a TIR 2900 % 11.4 11.4 21.1 18.9 21.1
18.7 21.2 .sup.2 TPS % 31.4 31.4 68.4 52.2 68.4 52.2 71.2 H.sub.2 O
% <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 PLA 32.6
.sup.10 CAc % 68.6 63.6 32.6 21.0 -- 21.0 -- .sup.4 Polyamide 1 --
-- 26.8 -- -- -- .sup.5 Polyester 1 -- -- -- -- 26.8 10.0 .sup.6
PCL % -- 5.0 -- -- -- 14.8 .sup.7 Extrusion ZSK ZSK ZSK ZSK ZSK ZSK
ZSK 40 40 40 40 40 40 40 T.degree. C. 210 210 195 195 185 195 205
Pressure bar 9 8 6.5 6 7 6.5 8.5 MFR g/10' 8.5 9.5 9.5 10 8.5 9 8.0
Granules 4 mm 4 mm 4 mm 4 mm 4 mm 4 mm 4 mm Granules H.sub.2 O %
0.1 0.2 0.2 0.1 0.2 0.2 0.3 Application Blown film - - - - - - +
Flat film + + + + + + - Sheets + + + + + + + Injection + + + + + +
- molding Fibers - - - - - - -
TABLE 4 Example 22 .sup.1 Starch % 2.0 .sup.1a TIR 2900 % 1.4
.sup.2 TPS % 3.4 .sup.3 PLA -- .sup.10 CAc % -- .sup.4 Polyamide 1
-- .sup.5 Polyester 1 59.0 .sup.6 PCL % 35.6 H.sub.2 O % <0.1
.sup.7 Extrusion ZSK 40 T.degree. C. 170 Pressure bar 6 MFR g/10'
10 Granules 4 mm Gra H.sub.2 O % 0.1 Application Blown film + Flat
film + Sheets - Injection molding - Fibers - Key: .sup.1 Starch =
native potato starch, dried, 3.5% H.sub.2 O: plasticizer 1a-1f
Bayer polymers as listed below. .sup.2 TPS = thermoplastic starch =
starch + plasticizer <0.1% H.sup.2 O, - water proportion by
devolatilization, based on EP 0 397 819 .sup.3 PLA (polylactic acid
resin) = Mitsui Toatsu Chemicals LACEA H 100 MFR 13 190.degree. C.
2.16 kg .sup.4 Polyamide 1 = Bayer BAK 1095 polyester amide MFR 2.5
150.degree. C. 2.16 kg .sup.5 Polyester 1 = BASF ZK 242/108
copolyester made from aliphatic diols and aliphatic/aromatic
dicarboxylic acids MFR 3.0 at 190.degree. C./2.16 kg .sup.6 PCL
(polycaprolactone) = Union Carbide Tone Polymer P-787 MFR 1.0
1.25.degree. C. 44 psi g/10 min .sup.7 Extrusion equipment = Werner
& Pfleiderer ZSK 40 MFR 150.degree. C., 10 kg .sup.10 CAc
cellulose diacetate DS 2.5
The materials termed TIR 2900-TIR 2908 are polyester amide products
from Bayer, with the following properties:
TIR 2900 is a polyester amide with an ester proportion of 48.5% by
weight made from adipic acid and 1,4-butanediol, and an amide
proportion of 41.2% by weight made from polycaprolactam, and also
10.3% by weight of stearic acid, based on the total mix. The
product has a relative solution viscosity of 1.29, measured at 0.5%
strength in m-cresol.
TIR 2901 is a polyester amide with an ester proportion of 29.8% by
weight made from adipic acid and 1,4-butanediol, and an amide
proportion of 56.1% by weight made from polycaprolactam, and also
14.1% by weight of stearic acid, based on the total mix. The
product has a relative solution viscosity of 1.25, measured at 0.5%
strength in m-cresol.
TIR 2905 is an ester made from 58.2% by weight of citric acid and
41.8% by weight of glycerol, with an average molecular weight of
about 600 g/mol.
TIR 2906-A is an ester made from 48.6% by weight of glycerol and
51.4% by weight of adipic acid, with an average molecular weight of
about 500 g/mol.
TIR 2907-A is a polyester amide with an ester proportion of 32.3%
by weight, made from adipic acid and glycerol and an amide
proportion of 54.1% by weight, made from polycaprolactam, and also
13.6% by weight of stearic acid, based on the total mix. The
product has a relative solution viscosity of 2.00, measured at 0.5%
strength in m-cresol.
TIR 2908 is a polyester amide with an ester proportion of 42.0% by
weight made from adipic acid and 1,4-butanediol, and an amine
proportion of 58.0% by weight made from polycaprolactam, based on
the total mix. The product was dissolved at 15% strength in
caprolactam at 90.degree. C. and then cast onto a plate, cooled
with dry ice and comminuted. The material was heated to reflux four
times at about 20% strength in acetone. The solution was poured
into a vat, with vigorous stirring, and diluted with again about
the same amount of acetone, and the precipitate was filtered off
with suction and dried in a vacuum drying cabinet at from 30 to
40.degree. C. The product has a relative solution viscosity of
2.12, measured at 0.5% strength in m-cresol.
Injection moldings, extrudates and films produced using polymer
mixtures proposed according to the invention have, besides
relatively good material properties, excellent biodegradability and
therefore are capable of making a substantial contribution to the
acute problem of waste. For example, films produced from a polymer
mixture proposed according to the invention have excellent
suitability for a wide variety of applications in the agricultural
sector, for example for covering fields, but films of this type
after their use can either be composted or ploughed into the earth
in the field. Polymer mixtures of this type are also suitable for
producing composting sacks, containers for waste for composting,
etc. In addition, it is possible to produce, for example,
containers and bottles from the polymer mixture proposed according
to the invention, using blow molding.
The rate of degradation can be influenced by the selection of the
polymer components.
The novel polymer mixtures are, however, also suitable for
producing textile products, for example for producing fibers,
monofilaments, sheet materials, such as wovens, felts, nonwovens,
backsheets, composite textile materials, flocks and waddings, and
also linear products, such as fibers, yarns, ropes, cords, etc. In
particular, it has been shown in practice that the novel polymer
mixtures are suitable for producing hygiene items, such as diapers,
bandaging and sanitary napkins, incontinence products, and also bed
inserts. The structure of these hygiene items has, inter alia,
nonwovens produced from the novel polymeric material, since this
has very good skin compatibility, is breathable and permeable to
water vapor, and at the same time waterproof, but together with
this is completely biodegradable.
The novel fibers are also suitable for producing filter materials,
such as in particular cigarette filters.
Many of the polymer mixtures proposed according to the invention,
such as in particular comprising thermoplastic starch and,
respectively, a copolyester and/or a polyester amide and/or a
polyester urethane, are also suitable as an adhesive, or else can
be used as coatings, for example for impregnating textile webs. It
has been found here that the polymer mixtures proposed according to
the invention and suitable for these application sectors are
preferably at least to some extent prepared and applied as
solutions in alcoholic solvents. For example, it was surprisingly
found, in the context of some experiments carried out as examples,
that the polymer mixtures prepared in this way are soluble in a hot
alcohol-ethanol mixture. In this case, too, a possible use became
apparent in the sense of a biodegradable adhesive, as a coating or
impregnation, which gives hydrophobic properties and is permeable
to water vapor.
Solvents which have proven suitable, besides alcohols, are ketones,
ethers, halogenated or halogen-free hydrocarbons and esters.
Preference is given to the use of acetone, ethyl acetate,
isopropanol, methanol, dichloromethane, chloroform,
tetrahydrofuran, ethanol or toluene. According to the invention,
the concentrations of the solutions are from 70 to 1% by weight
proportion of polymer, preferably from 50 to 8% by weight
proportion of polymer, particularly preferably from 40 to 19% by
weight proportion of polymer.
Using this method it is therefore possible to prepare solutions of
compostable adhesives which can be used for adhesive bonding, for
example using suitable adhesive bonding equipment and preferably at
temperatures in the order of from 60 to 100.degree. C. By applying,
for example, reduced pressure to accelerate removal of the solvent,
or by adding crystallization accelerators, the bonding procedure
can be accelerated. The novel adhesives can be used for adhesive
bonding of, for example, leather, ceramics, wood, board, paper or
plastics.
A still further application of the thermoplastic starch specified
according to the invention or of the polymer mixtures based on
thermoplastic starch is the production of flexible packaging
consisting of paper and of a film made from the novel material, by
laminating the paper with the film via high-temperature
calendering. This composite made from paper and bioplastic film can
readily be printed and is biodegradable and suitable for producing
flexible packaging for food and non-food sectors.
High-quality wall coverings, so-called vinyl wallcoverings, are
produced by coating with a PVC plastisol in a screen-printing or
gravure-printing process. The emission problems and environmental
problems of products which comprise PVC have been known for a long
time. The novel polymer mixtures can be used to produce blown films
or flat films in a thickness, usual for the coating of
wallcoverings, of from 80 to 120 .mu.m, and this coating may, where
appropriate, comprise fillers and other additives, and be
adhesively bonded with the wallcovering paper by hot-sealing in a
calender device, and then printed a number of times, as is
known.
The significantly improved material properties of the novel polymer
mixtures, in particular in relation to high dimensional stability,
even under variable climatic conditions, give rise to applications
which have hitherto been unavailable to other high-quality
materials. A particular reason for this is that these novel
materials which have been newly developed are biodegradable, if the
surroundings and the environmental conditions meet certain
requirements. Another application is therefore the production of
equipment for military maneuvers and military exercises in the
defense sector. These have hitherto been produced from plastics
which cause the expected pollution of the environment after their
use, since, as is known, it is impossible to retrieve them, or to
retrieve them adequately. It is therefore advantageous if this
equipment for military maneuvers and military exercises can be made
from the novel biodegradable materials.
Again in the defense sector, so-called traverse aids and folding
roadways are known, and are widely used in civil sectors, as well
as in military sectors, in order to render impassable areas
traversable. Folding roadways are usually produced from metallic
materials and seldom from plastic. In theory, folding roadways
should be retrieved after the exercise or after their use, but in
practice this is not done since the folding roadways have been
distorted as a result of heavy traffic loading, in particular by
heavy freight vehicles and armored vehicles, and therefore have no
further use. In order that environmental pollution is reduced, even
in cases such as these, it is advantageous to use folding roadways
made from the high-strength bio-degradable materials proposed.
The polymer solutions proposed according to the invention may also
be used for the waterproofing of non-waterproof, compostable
articles, by coating these articles at temperatures above
60.degree. C., preferably above 70.degree. C. The non-waterproof
compostable articles may be: cellulose products, such as paper or
board, textile structures, such as fabrics or nonwovens, wood or
timber materials, starch-containing materials, such as starch foam
with or without biodegradable polymers as a partner in the blend,
films or moldings made from biodegradable materials, leather or
leather materials, chitin and/or products made therefrom. The novel
coatings are also suitable for paper coating. The novel coatings
can also be used for inhibiting the corrosion of metals. It is also
possible to provide disposable culinary implements, storage
containers or coffins with waterproof coatings. The layer thickness
of the coating is generally from 0.1 to 20 mm, preferably from 0.5
to 10 mm, in particular from 1 to 5 mm.
However, the novel polymeric materials based on thermoplastically
processable starch are, of course, also suitable for any number of
other applications, including, for example, disposable
injection-molded products, etc.
* * * * *